Regulation of mouse epididymal epithelium in vitro by androgens, temperature and fibroblasts

The epididymal epithelium provides the microenvironment for sperm maturation. However, the molecular basis of epididymal function is still poorly understood because of the limitations of in vivo systems. For this reason, we have developed an in vitro culture system for mouse epididymal epithelial cells. Cells were purified by enzymatic digestion and centrifugation through a Percoll gradient, and plated on inserts coated with a replacement basement membrane. Cultured cells maintained ultrastructural and immunocytochemical features of epithelia, but did not retain the androgen responsiveness of epididymal cells (as judged by androgen receptor detection and secretion of specific markers) unless cocultured with fibroblasts. The androgen receptor was detected in the nuclei of epididymal epithelial cells only when grown with epididymal fibroblasts in the subjacent chamber. Moreover, specific epididymal secretory proteins were secreted only when epithelial cells were cultured in the presence of both androgens and fibroblasts at 32 degrees C. These results highlight the importance of cell-cell interaction, as well as temperature regulation in the physiology of the epididymis. They also establish the existence of two independent pathways in the differentiation of these cells. The first, leading to the expression of epithelial characteristics, is fibroblast-independent, whereas the second, conferring tissue-specific features, depends upon coculture with fibroblasts.